The recovery, indexing and storage of core samples is routinely undertaken in connection with a wide variety of scientific and commercial activities including the study of the earth's geology, exploration for recovery of hydrocarbons and the mining of other minerals, and the analysis of construction sites, among many others. In the field of petroleum exploration and recovery, oil companies, oil field service companies, mining and environmental companies and agencies commonly deal with core samples.
The cores are typically cataloged and stored at a laboratory site and are individually subjected to a variety of tests and measurements by scientists and technicians. The processing known as “Routine Core Analysis” (RCAL) includes measurement of porosity, grain density, horizontal permeability, fluid saturation, and a lithologic description. Routine core analysis can also include a core gamma log and measurements of vertical permeability, which can be taken at room temperature and either at ambient pressure, formation confining pressure, or both. Routine core analysis is to be distinguished from “Special Core Analysis” (SCAL) in which relative-permeability and capillary pressure data are obtained, usually for the purpose of performing reservoir simulation analysis.
Data analysis and simulation methods have been developed to enable the user to allocate selected relative-permeability and capillary pressure curves to appropriate blocks in the simulation grid automatically by applying pre-determined criteria. Three-dimensional visualization capabilities provide a rapid and effective way of confirming and comparing data allocations.
In accordance with the methods of the prior art, a core is removed from a storage facility by a laboratory technician and is subjected to testing to provide RCAL and SCAL measurements and these measurements are entered into a database. In response to an inquiry for relevant RCAL and/or SCAL data, a technician views stored images, e.g., on a monitor linked to the database. One or more communications must then be exchanged with an expert in the lab and/or geologists for a description of the sample. A further common step is to return to the core storage facility to obtain the core layout and to then make a comparison between cores from two or more other wells or fields.
When considering the field of hydrocarbon exploration and production, the steps of subjecting the cores or core plugs to analysis in order to obtain values for the various characteristics mentioned above and storing them is solely for the purpose of having the data available in a form that can be used by other engineers and scientists who are studying the geological, petrophysical and geophysical information for a variety of purposes. The data collected as described above is stored in hard and soft databases.
Core data provides a highly reliable source of information about reservoir characteristics and can be used for significant geological interpretations. The prior art has developed the technology to permit users to view images of more than one database, e.g., of whole cores and of slabs, at their desktop computer monitors. However, data are typically indexed by well name, depth and formation. Core and plug data are conventionally stored as images. Even when optimized, the prior art procedures for completing conventional and special core analyses and thin section analysis can be time-consuming.
Catalogs of thin sections of rock have also been constructed. However, at present the user must undertake a comparative visual search of the catalog for each new thin section image to establish similarity. In other words, images must be browsed, one-by-one, in order to make the appropriate match. Users sometime experience difficulty in making the appropriate correlations.
It is also known to prepare variograms and histograms based on data collected from samples in order to further characterize the reservoir samples. Variogram models are also known that are based on data obtained empirically, or from actual tests performed on core samples.
Although the numerous measurements that have been customarily and routinely obtained are useful, alternative means for characterizing and storing data in a form that is rapidly retrievable and which can be correlated would be desirable. It would also be desirable to provide an improved method and system to enable users to more quickly and accurately locate, identify and correlate relevant images from existing databases.
It is therefore one object of the present invention to provide a method and apparatus for the efficient classification and correlation of cores and plugs utilizing a novel form of characterizing data.
Another object of the invention is to provide such an apparatus and method that is efficient in terms of time and the physical effort required to assemble and store the data in retrievable form and that can be easily correlated.
It is a further object of the present invention to provide an improved method and system for matching and retrieving core images and computerized tomography (CT) images.
Yet another object of the invention is to provide a system and method to store and retrieve image data based on the specific properties of cores and plugs and to reduce the time required to obtain the desired data and images.